The present invention relates to tension type dynamic viscoelasticity measuring apparatus.
In conventional devices of this kind, to avoid the effects of relaxation phenomena in connection with a change in length of the specimen due to stress relaxation and creep of the specimen, a movement control timing signal is generated at a predetermined time after the previous movement control, the predetermined time being irrelevant to the distance traveled by the moving mechanism.
Since in the above-mentioned prior art devices, the next movement control is performed after a predetermined time, which is unrelated to the distance traveled by the moving mechanism, if the predetermined time is set to be a relatively short time, it offers an advantage of quicker movement control but also gives rise to the following problem: when the amount of movement of the moving mechanism is large, the next movement control timing signal occurs while the specimen is still continuing to elongate, or contract, at a high rate due to the relaxation phenomena of the specimen, making the control unstable.
Conversely, when the predetermined time interval is set to be relatively long, the above drawback is eliminated but since the number of movement controls is reduced, the measurement takes longer. A further drawback associated with a relatively long predetermined time interval arises due to the fact that when the specimen temperature has reached a transition temperature such as a glass transition temperature, the specimen elongates or contracts not only by external forces resulting from movement but also by its own property. This could be remedied by a quick control action but since the control intervals are long, there may be times when the measurement cannot be taken at the transition point, the most important section of the measuring process.